How To Use Transparent Overlays

I just ordered ScrapSimple Transparent Overlays: Esprit. No directions on how to use. I want to fill each square with grandchildren pictures. I can't seem to find a tutorial for this.
I just know one of you will be able to tell me how to do this or where to find a tutorial to make this LO from scratch. Thank you for any help.

Create a new layer, under the overlay.
Use the marquee tool to select one square of the overlay.
Fill the selection with the paint bucket tool, make sure the new layer is selected
You can now clip your photo to the square you created (ctrl + G in Windows PSE)
Repeat as necessary.

There is probably a quicker way to do it, but this was the first that sprang to mind.

You could crop your photos to squares, then resize them once they are on your layout. The only thing to need to remember to do is duplicate your photo before you crop it, so you don't loose your original.

Here's another method that I like and use all the time. It sounds like a lot of steps, but after you've done it a few times, it's pretty simple.

1. Place a photo on the desired square, being sure the photo fills the square or is slightly larger.
2. In the layers palette drag the photo layer below the transparency/overlay layer
3. Activate (select) the transparency/overlay layer
4. Using the Magic Wand Tool, with the tolerance set to 32 and contiguous checked, click once inside the square (this puts marching ants around the square)
5. Go to Select>Inverse (Shift+Ctrl+I)
6. Activate the photo layer
7. Press Delete
8. Press Ctrl+D or Escape to deselect the marching ants

Select the magic wand tool, and set it to contiguous.
Click inside a photo square, you should see marching ants for its borders
Click Select menu, Modify, Expand and enter a number like 5 (pixels).
Click the New Layer button. Presto, a clipping mask for your photo.
Move the new layer below the overlay, and clip your photo to it. Repeat for each square where you'd like a photo.